The purpose of this project is: to examine the effects of diets high in sucrose and/or high in aspartame (Nutrasweet) on the behavior and cognitive performance of children. With this study, we intend to rigorously examine the possibility of adverse behavioral and/or cognitive effects from sugar and/or aspartame when they are consumed in large quantities over an extended period in the diets of children. Because both sugar and aspartame are widely used throughout the American food supply, this study has major implications for the health and behavior of children. Our examination will be rigorous by including: 1) randomization with a within-subject design; 2) blinding to the testing conditions of subjects, families, and researchers; 3) clear categorization with a variety of subjects; 4) employment of dependent measures that are comprehensive in the areas of child behavior and cognitive performance and both established and recognized for their validity and reliability; 5) employment of procedures to ensure compliance with the diets; and 6) sufficient power to provide valid results whether the null hypothesis is or is not supported. We will examine four cohorts of children: 1) normal school age (6 to 12 years of age) children; 2) school age children with the diagnosis of attention deficit hyperactivity disorder (DSM III-R); 3) school age children reported to respond adversely to increased quantities of refined sugars: and 4) normal preschool children (3-5 years of age). We will employ four diet conditions of one month duration each, in a Latin square design. The diets will be: 1) a diet high in sucrose with no aspartame; 2) a diet high in aspartame with no sucrose; 3) a diet high in sucrose and aspartame; and 4) a diet with no aspartame or sucrose. We will employ sham variables and weekly measures to create the appearance of change at non- change points as a further blinding procedure. During the 16-week study period, weekly measures of behavior and cognitive performance will be obtained. The measures will include those described as likely to be affected or those characteristic of hyperactivity, namely: 1) attention span; 2) activity level; and 3) impulsivity. In addition, we will measure learning abilities and academic performance. For each of the characteristic we will obtain multiple measures of that characteristic from different sources and in different situations (home, school, and laboratory). These will include: 1) subjective ratings obtained from parents and teachers; 2) information about actual school performance; 3) activity level as measured by actometer; and 4) performance on a battery of neuropsychological measures assessing vigilance and learning. We will also obtain blood samples at the end of the third week in each diet phase. These will be assessed for serum glucose and phenylalanine levels. We will collect urine samples weekly to assess markers in the diet (abscorbic acid and riboflavin) confirming compliance.